1. Field of the Invention
This invention relates to a catalyst component or catalyst that is useful for the stereoregular polymerization or copolymerization of alpha-olefins and more particularly concerns a magnesium-containing supported titanium-containing catalyst component or catalyst that is useful for producing a homopolymer or copolymer of an alpha-olefin.
2. Discussion of the Prior Art
Although many polymerization and copolymerization processes and catalyst systems have been described for polymerizing or copolymerizing alpha-olefins, it is highly desirable to develop a catalyst component or a catalyst that has improved activity for catalyzing such reactions. It is also advantageous to tailor a process and catalyst system to obtain a specific set of properties of a resulting polymer or copolymer product. For example, commercial alpha-olefin polymerization or copolymerization, especially gas-phase alpha-olefin polymerization or copolymerization, requires additional catalyst attributes for economical large-scale operation. Specifically, polymer or copolymer morphology is often critical and typically depends upon catalyst morphology. Good polymer morphology generally involves uniformity of particle size and shape, a narrow particle size distribution, resistance to attrition and an acceptably high bulk density. Minimization of very small particles (fines) typically is very important, especially in gas-phase polymerizations or copolymerizations in order to avoid transfer or recycle line plugging. From the standpoint of polymerization process efficiency, high levels of small polymer particles can cause problems because the particles tend to accumulate in, and plug, process lines and filters. From the standpoint of handling and processing of polyolefins, small polymer particles and broad particle size distribution can be disadvantageous because polymer bulk density often is lower than desired and an extrusion and/or pelletization step often is required prior to processing.
Therefore, it is highly desirable to develop alpha-olefin polymerization and copolymerization catalysts and catalyst components that have improved morphology. For example, experience indicates that, in order to produce high ethylene content/high melt flow rate impact copolymers of ethylene and propylene having a median particle size of at least 1000 microns, it is necessary to employ a copolymerization catalyst having a median particle size of at least 35-55 microns. Another property which is important commercially is the maintenance of an acceptably high bulk density. Typically, this property is measured in pounds per cubic foot of polymer or copolymer. Also important is maintaining low atactic levels such as measured by hexane soluble and extractable materials formed during polymerization or copolymerization.
Magnesium-containing supported titanium halide-based alpha-olefin polymerization or copolymerization catalyst components or catalyst systems containing such components are now well known in the art. Typically, these catalyst components and catalyst systems are recognized for their performance based on activity and stereospecificity. However, commercial olefin polymerization or copolymerization requires additional catalyst attributes for economical large-scale operation. In particular, it is highly desirable to develop a catalyst, or catalyst component, or a method for producing such catalyst or catalyst component, that could be modified readily so that the resulting catalyst or catalyst component could have a wide range of catalytic activities or could be used to produce a wide range of polymers and copolymers having different sets of properties.
Numerous individual processes or process steps have been disclosed which have as their purpose the provision of improved supported, magnesium-containing, titanium-containing, electron donor-containing olefin polymerization or copolymerization catalysts. More particularly, Arzoumanidis et al., U.S. Pat. Nos. 4,866,022; 4,988,656; and 5,013,702 disclose a method for forming a particularly advantageous alpha-olefin polymerization or copolymerization catalyst or catalyst component that involves a specific sequence of specific individual process steps such that the resulting catalyst or catalyst component has exceptionally high activity and stereospecificity combined with very good morphology. A solid hydrocarbon-insoluble, alpha-olefin polymerization or copolymerization catalyst or catalyst component with superior activity, stereospecificity and morphology characteristics is disclosed as comprising the product formed by 1) forming a solution of a magnesium-containing species from a magnesium hydrocarbyl carbonate or magnesium carboxylate; 2) precipitating solid particles from such magnesium-containing solution by treatment with a transition metal halide and an organosilane as a morphology controlling agent; 3) reprecipitating such solid particles from a mixture containing a cyclic ether; and 4) treating the reprecipitated particles with a transition metal compound and an electron donor. In U.S. Pat. Nos. 4,866,022; 4,988,656; and 5,013,702, this treatment in the fourth step was performed at either 135.degree. C., 137.degree.-143.degree. C. or 120.degree. C. in Examples 1-17 or initially at 110.degree. C. and then at 93.degree.-96.degree. C. in Example 18, or initially at 130.degree. C. for 90 minutes and then heating was stopped for the next 8 minutes in Example 20. Alcohols that are useful in solvating magnesium carbonates are disclosed in column 4, lines 36-44 of U.S. Pat. No. 4,866,022 as including: "those having the structure HOR' wherein R' is an alkyl radical of 1 to about 18 carbon atoms, an aryl radical of 6 to about 12 carbon atoms or an alkaryl or aralkyl radical of 7 to about 12 carbon atoms. Typically, one or more alcohols containing from 1 to 12 carbon atoms can be used such as methanol, ethanol, propanol, isopropanol, tert-butyl alcohol, cyclohexanol, 2-ethylhexanol, dodecanol, and the like. Of these, 2-ethyl-1-hexanol is preferred." The ratio of the total number of moles of the alcohol employed-to-the magnesium hydrocarbyl carbonate or carboxylate from which the magnesium-containing species is formed in the examples in U.S. Pat. No. 4,886,022 is 1.32:1.
Arzoumanidis et al., U.S. Pat. No. 4,540,679 discloses a process for the preparation of a magnesium hydrocarbyl carbonate by reacting a suspension of a magnesium alcoholate in an alcohol with carbon dioxide and reacting the magnesium hydrocarbyl carbonate with a transition metal component. Sufficient alcohol is employed to form a solution of the resulting magnesium hydrocarbyl carbonate in the alcohol. The ratio of the total number of moles of the alcohol employed-to-the magnesium alcoholate in the examples in U.S. Pat. No. 4,540,679 is 3.9:1 to 10.5:1.
Arzoumanidis et al., U.S. Pat. No. 4,612,299 discloses a process for the preparation of a magnesium carboxylate by reacting a solution of a hydrocarbyl magnesium compound with carbon dioxide to precipitate a magnesium carboxylate and reacting the magnesium carboxylate with a transition metal component. Alcohols are not disclosed as suitable for use as a solvent or diluent in the process disclosed therein.
While each of the processes of the aforesaid U.S. Pat. Nos. 4,540,679; 4,612,299; 4,866,022; 4,988,656; and 5,013,702 affords alpha-olefin polymerization or copolymerization catalysts or catalyst components which have improved morphology and which afford polymer or copolymer products which also have improved morphology, it is highly desirable to develop additional alpha-olefin polymerization or copolymerization catalysts or catalyst components that have even further improved morphology and that afford polymers or copolymers, especially the aforesaid impact copolymers, which also have even further improved morphology.
Cohen et al., U.S. Pat. No. 4,946,816 discloses the addition of a C.sub.8 -C.sub.10 aromatic compound to the solvent in any of the aforesaid steps Nos. 1), 2) or 3) of the aforesaid U.S. Pat. Nos. 4,866,022; 4,988,656; 5,013,702; 4,540,679; and 4,612,299, at any time prior to the addition of ether in the aforesaid step 3), in order to control the morphology of the final particles of the resulting catalyst or catalyst component. Particular C.sub.8 -C.sub.10 aromatic compounds that are suitable morphology control agents include o-xylene, m-xylene, p-xylene, mixed xylenes, ethylbenzene, naphthalene, cumene, pseudocumene, methylethyl benzenes, tetrahydronaphthalene, and diethylbenzenes. Ethylbenzene, orthoxylene, metaxylene, paraxylene and naphthalene are preferred. Mixtures of C.sub.8 -C.sub.10 aromatic compounds may also be used. Naphthalene is most preferred. Preferably the C.sub.8 -C.sub.10 aromatic compound is introduced in step 2) of the method of their invention, although such aromatic compound may also be introduced in step 1) of the method of their invention or in step 3) before addition of the cyclic ether. Typically, from about 1000 to about 20,000 parts by weight or 0.1-2 wt. % of such C.sub.8 -C.sub.10 aromatic compound per million parts of the total amount of material present are incorporated within the solvent to effect the desired morphology change. Preferably, about 2000 to about 10,000 parts per million of such C.sub.8 -C.sub.10 aromatic compound are used. For a solvent incorporating only a C.sub.8 aromatic compound, the most preferred range is about 4000 to about 10,000 of the C.sub.8 aromatic compound.
Arzoumanidis, Drezdzon and Lee, pending U.S. patent application Ser. No. 07/624,210, filed Dec. 7, 1990 and now U.S. Pat. No. 5,124,297, disclose a catalyst or component and a method of production thereof, which are based on the catalyst or catalyst component and method of production thereof, respectively, of the aforesaid U.S. Pat. Nos. 4,540,679; 4,612,299; 4,866,022; 4,988,656; and 5,013,702, wherein the resulting catalyst or catalyst component has a relatively larger median particle size and a relatively narrower particle size distribution and is particularly effective for the production of homopolymers of propylene and copolymers of propylene and ethylene, especially high ethylene content/high melt flow rate impact copolymers of propylene and ethylene, which homopolymers and copolymers have a relatively larger medium particle size and a relatively narrower particle size distribution. The key additional feature of the method of U.S. patent application Ser. No. 07/624,210 (now U.S. Pat. No. 5,124,297) is that the solution of the magnesium-containing species that is formed comprises at least one alcohol containing from 1 to about 18 carbon atoms at a ratio of the total number of moles of the at least one alcohol-to-the number of moles of the aforesaid magnesium-containing compound in the range of from about 1.45:1, preferably from about 1.6:1, to about 2.3:1, preferably to about 2.1:1. Alcohols that are suitable for use in the method of U.S. patent application Ser. No. 07/624,210 include those having the structure HOR wherein R is an alkyl radical of 1 to about 18 carbon atoms, an aryl radical of 6 to about 12 carbon atoms or an alkaryl or aralkyl radical of 7 to about 12 carbon atoms. Typically, one or more alcohols containing from 1 to 12 carbon atoms can be used, such as ethanol, 1- or 2-propanol, t-butyl alcohol, cyclohexanol, 2-ethylhexanol, the amyl alcohols including isoamyl alcohol, and the branched alcohols having 9 to 12 carbon atoms. Preferably, 2-ethylhexanol and/or ethanol is employed.
All or only a portion of the total amount employed, or any component of the at least one alcohol employed in the method of U.S. patent application Ser. No. 07/624,210 (now U.S. Pat. No. 5,124,297), can be present in the aforesaid liquid when the magnesium-containing species is formed from the magnesium-containing compound or when the magnesium-containing species is dissolved in the aforesaid liquid in the aforesaid step 1. In the alternative, all or a portion of the at least one alcohol employed, or any component thereof, can be added to the aforesaid liquid after the magnesium-containing species is formed from the magnesium-containing compound or after the magnesium-containing species is dissolved in the aforesaid liquid, but the total amount of the aforesaid at least one alcohol must be added before or when the solid particles are being precipitated in the aforesaid step 2 in the aforesaid U.S. Pat. Nos. 4,540,679; 4,612,299; 4,866,022; 4,988,656; and 5,013,702, except when the solid particles are reprecipitated.
Preferably, in the method of U.S. patent application Ser. No. 07/624,210 (now U.S. Pat. No. 5,124,297), the at least one alcohol comprises a combination of a relatively lower molecular weight monohydroxy alcohol containing from 1 to 4 carbon atoms and a relatively higher molecular weight monohydroxy alcohol containing from 5 to about 18 carbon atoms, and at a ratio of the number of moles of the relatively lower molecular weight alcohol-to-the total number of moles of total alcohols in the range of from about 0.45:1, preferably from about 0.5:1, to about 0.85:1, preferably to about 0.8:1. Preferably, the relatively lower molecular weight alcohol is ethanol and the relatively higher molecular weight alcohol is 2-ethylhexanol or an amyl alcohol. Therefore, as indicated hereinabove, all or a portion of either or both components of this combination can be present in the aforesaid liquid when the magnesium-containing species is formed from the magnesium-containing compound or when the magnesium-containing species is dissolved in the aforesaid liquid in the aforesaid step 1 in the aforesaid U.S. Pat. Nos. 4,540,679; 4,612,299; 4,866,022; 4,988,656; and 5,013,702, or can be added to the aforesaid liquid after the magnesium-containing species is formed from the magnesium-containing compound or after the magnesium-containing species is dissolved in the aforesaid liquid.
The benefits resulting from the use of the aforesaid at least one alcohol to produce the catalyst or catalyst component in the method of U.S. patent application Ser. No. 07/624,210 (now U.S. Pat. No. 5,124,297) at a level in the range of from about 1.45 to about 2.3 total moles of the at least one alcohol per mole of the magnesium-containing compound are (1) the production of a reduced number of catalyst fines and hence of small polymer or copolymer particles produced using such catalyst or catalyst component; and (2) the production of catalyst or catalyst component having a relatively larger mean particle size and relatively narrower particle size distribution the use of which affords polymer or copolymer also having a larger mean particle size and improved particle size distribution and bulk density; (3) a substantially less viscous solution in the aforesaid step 1 in the aforesaid U.S. Pat. Nos. 4,540,679; 4,612,299; 4,866,022; 4,988,656; and 5,013,702. These benefits are further enhanced by the use of the aforesaid combination of the relatively lower and relatively higher molecular weight alcohols.
Nevertheless, it is highly desirable to develop an improved method for the manufacture of a catalyst or catalyst component for the polymerization or copolymerization of alpha-olefins, in which the catalyst or catalyst component produced not only has a relatively large medium particle size and relatively narrow particle size distribution but also has a more uniform, especially substantially spheroidal, particle shape and is more resistant to attrition and therefore does not need to be prepolymerized. Good polymer morphology also involves uniformity of particle shape, preferably substantially spheroidal. Thus, it is highly desirable to develop alpha-olefin polymerization and copolymerization catalysts and catalyst components that have uniform particle shape, preferably spheroidal, and resistance to attrition. Attrition of catalyst or catalyst component particles having a relatively large median particle size and/or a uniform shape, results in the formation of particles, especially fines, of the catalyst or catalyst component having a smaller medium particle size and a nonuniform particle shape and a broadening of the particle size distribution of the catalyst or catalyst component. The additional step of prepolymerization of the catalyst or catalyst component with an alpha-olefin is often preferred or even essential in order to improve the attrition resistance of the particles of the catalyst or catalyst component before use as a polymerization or copolymerization catalyst or catalyst component. It is also highly desirable to eliminate the need to prepolymerize the catalyst or catalyst component before using it as a polymerization or copolymerization catalyst or catalyst component.
Both Terano, Soga, and Inoue, Japanese Kokai No. 63105007 (May 10, 1988) and Terano and Soga, Japanese Kokai No. 91,227,309 (Oct. 8, 1991) disclose the use of some form of a temperature reduction during or after activation of a solid catalyst component for use in olefin polymerization. For example, in Example 1 in Japanese Kokai No. 63105007, magnesium metal, iodine and n-butylchloride were mixed below the boiling temperature of n-butylchloride, and the resulting solids were washed with n-butylchloride. The washed solids were then mixed with di-n-butylphthalate and titanium tetrachloride, and the mixture was ball milled. The ball milled solids were next activated twice with toluene and titanium chloride at 115.degree. C. for 2 hours for each activation. The activated solids were then cooled to 40.degree. C. and washed with heptane. Similarly, in Example 1 in Japanese Kokai No. 91,227,309, magnesium ethoxide toluene and titanium tetrachloride were heated at 70.degree. C., butanol was added to the mixture; and then the temperature was raised to 90.degree. C. and phthaloyl dichloride was added to the mixture. The resulting mixture was then mixed at 115.degree. C. for 2 hours, after which time the solids were separated and washed with toluene. The resulting solids were then activated three times with toluene and titanium tetrachloride at 115.degree. C. for 2 hours for each activation. The activated solids were washed with heptane at 40.degree. C.